A hair deforming treatment agent comprising the following components (A), (B) and (C): (A) glyoxylic acid, or a hydrate or a salt thereof, (B) a compound represented by the following formula (1): wherein R 1 represents H or a methyl group, A 1 , A 2 and B each represent H, an alkyl group, an alkenyl group, etc., D represents H, OH, a methyl group, an alkoxy group, etc., and E represents H, a methyl group, an alkoxy group, etc., and (C) water.
